地质通报2016，Vol.35Issue(5)：711-726,16.
海原断裂干盐池探槽揭示非特征性古地震序列
Research on various magnitudes of paleoearthquakes：A case study of non-characteristic earthquakes from the Salt Lake site of Haiyuan fault
摘要
Abstract
The active left-lateral Haiyuan fault is one of the major continental strike-slip faults in the Tibetan Plateau. The last large earthquake that occurred on the fault was the great 1920 Ms 8½ Haiyuan earthquake with a 230-km-long surface rupture and maxi⁃mum left-lateral slip of 10.2m. Much less known is its earthquake recurrence behavior in spite of much focused studies. The current understanding is still preliminary and requires validation of paleoseismic data based on fine stratigraphy in trenching. In this study, the authors present results of a paleoseismic study at the Salt Lake site in a shortcut pull-apart basin within the section that broke in 1920. 3D excavation at the site exposed fine-grained and layered stratigraphy and ample evidence of multiple paleoseismic events. Charcoal fragments are abundant in the trenches. AMS dating of charcoal fragments shows that multiple events occurred during the past 3600 years. Of these, the youngest three and possibly four events were recorded in the top 2.5m section of distinctive thinly-layered stratig⁃raphy. A comparison of paleoseismic with historical earthquake records suggests that these three events are correlative to the AD 1920, 1760 (or 1709) and 1638 earthquakes. Historical accounts of earthquake damage suggest that earthquakes exposed in the trench⁃es are markedly different in magnitude. With the exception of the most recent M8 earthquake in AD 1920, two earlier events were considerably smaller, with magnitude M<7, and more likely M6 or less. Thus, the Haiyuan fault could produce surface-rupturing earthquakes with a variety of magnitudes, not just characteristic earthquakes. This study indicates that paleo-earthquakes exposed in trenches are not necessarily similar in size, and moderate magnitude events might produce surface ruptures, which can be preserved in stratigraphy and exposed in a paleoseismic trenching under some conditions, for instance, the sedimentation is fast enough and there exists no hiatus in deposition.关键词
海原断裂/干盐池/古地震/历史地震/非特征型地震Key words
Haiyuan fault/Salt Lake/paleoearthquake/historical earthquake/non-characteristic earthquake分类
天文与地球科学引用本文复制引用
邵延秀,刘静,Yann Klinger,谢克家,袁道阳,雷中生..海原断裂干盐池探槽揭示非特征性古地震序列[J].地质通报,2016,35(5):711-726,16.基金项目
中国地震局行业专项（编号201208006）、国家自然科学基金项目（批准号41225010）和地震动力学国家重点实验室自主课题 （）
